Method for inhibiting hydrate formation

Abstract

A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents is disclosed. More specifically, the method can be used in treating a petroleum fluid stream such as natural gas conveyed in a pipe to inhibit the formation of a hydrate restriction in the pipe. The hydrate inhibitors used for practicing the method are substantially water soluble polymers formed from a N-substituted acrylamide having two nitrogen substituent groups, R 1 and R 2 , where R 1 is a hydrocarbon group having from one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and combinations thereof, and R 2 is a hydrogen atom or a hydrocarbon group having from one to ten carbon atoms selected from the group consisting of carbon, nitrogen, oxygen, and sulfur; alternatively, R 1 and R 2 may be linked to produce a cyclic ring having ten atoms comprising a combination of between three and ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and combinations thereof. Some examples of such inhibitors include, but are not limited to, poly(N-ethylacrylamide), poly(N,N-diethylacrylamide), poly(N-methyl, N-acrylamide), poly(iso-propylacrylamide), poly(n-propylacrylamide), poly(N-cyclopentylacrylamide), poly(N-cyclohexylacrylamide), poly(acryloylpiperdine), poly(acryloylpiperdine), poly(acryloylmorpholine) and various N-substituted acrylamide copolymers.

We claim: 
     
       1. A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents, said method comprising treating said fluid with an inhibitor comprising a substantially water soluble polymer having the following N-substituted acrylamide: ##STR10## where, R 1  is a hydrocarbon group having one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and, combinations thereof, R 2  is hydrogen atom or a hydrocarbon group having one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, and combinations thereof, and,   x is an average number of repeating monomeric units for producing an average molecular weight for said polymer between about 1,000 and about 6,000,000 for said polymer.   
     
     
       2. The method of claim 1 wherein R 1  is an alkyl, cycloalkyl, aryl, alkaryl, or aralkyl group having said zero to four heteroatoms and R 2  is a hydrogen atom or an alkyl, cycloalkyl, aryl, alkaryl, or aralkyl group having said zero to four heteroatoms. 
     
     
       3. The method of claim 1 wherein R 1  is an alkoxyalkyl, alkenyl, or alkynyl group having said zero to four heteroatoms and R 2  is an alkoxyalkyl, alkenyl, or alkynyl group having said zero to four heteroatoms. 
     
     
       4. The method of claim 1 wherein R 1  and R 2  are linked to produce a cyclic moiety having up to ten atoms comprising a combination of between three and ten carbon atoms and said zero to four heteroatoms. 
     
     
       5. The method of claim 1 wherein said N-substituted acrylamide produces a polyalkylacrylamide selected from the group consisting of poly(iso-propylacrylamide), poly(n-propylacrylamide), poly(N-cyclopentylacrylamide), poly(N-cyclohexylacrylamide), copolymers formed from N-substituted acrylamides, and mixed copolymers formed from N-substituted acrylamides and monomers selected from the group consisting of vinylpyrrolidone, vinylcaprolactam, vinyloxazoline, acrylates, and vinyl carboxylates. 
     
     
       6. The method of claim 2 wherein said N-substituted acrylamide produces a polyalkylacrylamide selected from the group consisting of poly(acryloylpyrrolidine), poly(acryloylpiperdine), poly(acryloylmorpholine) copolymers formed from N-substituted acrylamides, and mixed copolymers formed from N-substituted acrylamides and monomers selected from the group consisting of vinylpyrrolidone, vinylcaprolactam, vinyloxazoline, acrylates, and vinyl carboxylates. 
     
     
       7. The method of claim 1 wherein said inhibitor further comprises a substantially water soluble polymer selected from the group consisting of polyvinylpyrrolidone, polyvinylcaprolactam, and N-acyl substituted polyalkeneimines. 
     
     
       8. A method for inhibiting the formation of clathrate hydrates in a fluid having hydrate forming constituents, said method comprising: treating said fluid with an inhibitor mixture having, a) an inhibitor comprising a substantially water soluble polymer having the following N-substituted acrylamide: ##STR11##  where, R 1  is a hydrocarbon group having one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and, combinations thereof, R 2  is hydrogen atom or a hydrocarbon group having one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, and combinations thereof, and,   x is an average number of repeating monomeric units for producing an average molecular weight for said polymer between about 1,000 and about 6,000,000 for said polymer, and;   b) a liquid used for introducing said inhibitor into said fluid.       
     
     
       9. The method of claim 8 wherein said N-substituted acrylamide produces a polyalkylacrylamide selected from the group consisting of poly(N-methylacrylamide), poly(N-ethylacrylamide), poly(N,N-diethylacrylamide), poly(N-methyl,N-ethylacrylamide),poly(isopropylacrylamide), poly(n-propyl acrylamide), poly(N-cyclopentylacrylamide), and poly(N-cyclohexylacrylamide), copolymers formed from N-substituted acrylamides, and mixed copolymers formed from N-substituted acrylamides and monomers selected from the group consisting of vinylpyrrolidone, vinylcaprolactam, vinyloxazoline, acrylates, and vinyl carboxylates. 
     
     
       10. The method of claim 8 wherein R 1  is selected from the group consisting of an alkyl group and a cycloalkyl group and R 2  is selected from the group consisting of hydrogen, an alkyl group, and a cycloalkyl group. 
     
     
       11. The method of claim 8 wherein said inhibitor mixture further comprises a substantially water soluble polymer selected from the group consisting of polyvinylpyrrolidone, polyvinylcaprolactam, and N-acyl substituted polyalkeneimine. 
     
     
       12. The method of claim 8 wherein said liquid is selected from the group consisting of an alcohol, water, and brine. 
     
     
       13. The method of claim 8 wherein R 1  and R 2  are linked to produce a cyclic moiety having up to ten atoms comprising a combination of between three and ten carbon atoms and said zero to four heteroatoms. 
     
     
       14. A method for inhibiting the formation of clathrate hydrates in a pipe containing a petroleum fluid stream having hydrate forming constituents, said method comprising: a) producing an inhibitor mixture having, 2) an inhibitor comprising comprising a substantially water soluble polymer produced from the following N-substituted acrylamide: ##STR12## where, R 1  is a hydrocarbon group having one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, sulfur, and, combinations thereof,     R 2  is hydrogen atom or a hydrocarbon group having one to ten carbon atoms and zero to four heteroatoms selected from the group consisting of nitrogen, oxygen, and sulfur, and combinations thereof, and,   x is an average number of repeating monomeric units for producing an average molecular weight for said polymer between about 1,000 and about 6,000,000 for said polymer, and; 2) a liquid used for used for introducing said inhibitor into said fluid; and     b) introducing said inhibitor mixture into said petroleum fluid stream, thereby inhibiting the formation of a hydrate restriction in said pipe.